Longitudinal slipper die for extruding organic plastics



May 7, 1946.

J. BAILEY ETAL v LONGITUDINAL SLIPPER DIE FOR EXTRUDINGQ ORGANIC PLASTICS Filed Nov. 9, 1944 2 Sheets-Sheet 1 w a W Y Z W, a b m r In 6 w \h w k h M liflik\ 3 Wit e WEZT May 7, 1946- J. BAILEY ETAL LONGITUDINAL SLIPPER DIE FOR EXTRUDING ORGANIC PLASTICS 2 Sheets-heet 2 Filed Nov. '9 1944 E M? m a? Patented May 7, 1946 UNITED STATES DONGITUDINAL SLIPPER DIE FOB EXTRUDING ORGANIC PLASTICS James Bailey, West Hartford, and Herbert A.

Pratt, Hartford, Conn., assignors to Pia: Corporation, Hartford, Conn., a corporation of Delaware Application November 9, 1944, Serial No. 502,000 4 Claims. (Ci. 18-12) This invention relates to apparatusfor forming shapes of organic plastic materials by extrusion and has particular relation to the extrusion of shapes, such as relatively thick shapes, which cannot vbe formed in ordinary extrusion dies because of excessive friction or sticking.

The general object or the invention is to provide a novel apparatus whereby sticking or fric tion of a shape in an extrusion die is overcome in a simple and practical way.

More specifically it is an object of the invention to provide a novel apparatus of the above kind for extrusion oi shapes which are substantially hardened and made self-sustaining in the extrusion die in order that they may be accurately formed to the shape of the die, which apparatus is characterized by the provision of a split die, the parts of which ar reciprocated longitudinally of the extruded abs and in opposite directions to each other during the extruding operation.

Another object of the invention is to provide a novel longitudinal slipper die for extruding organic plastics in which provision is made for maintaininm film of lubricant between the shape formed in the die and the die surfaces.

Other objects and advantages of the invention will be pointed out in the following specification or will become apparent therefrom, or from the accompanying drawings which illustrate an embodiment of the invention, and in which drawhiss Figure l is a view in longitudinal sectional elevation of the novel apparatus;

Fig. 2 is a view of the apparatus in rear sectional elevation taken approximately on the line 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a view in transverse section taken approximately on the line 3-8 of Fig. 1, looking in the direction of the arrows; and

Fig. 4 is a partial. view in horizontal sectional top plan of the extrusion nozzle and associated die members. Y

Referring now to the drawings. it will be seen from Fig. 1 that organic plastic material is received by the nozzle i from a pipe 6 and discharged from the nozzle between longitudinal slipper die members I and I between which the shape t is formed in die opening is. The plastic material may be supplied in heated condition by a suitable ram or stuifer (not shown) The nozzle I and the slipper die members! and I are supported by a bed plate ll bolted to a frame II. as shown. The nozzle is bolted to a block II which in turn is secured to the rear end oi the bed plate Ii, and the pipe 6 is clamped to the nozzle by a screw it in clamp II on studs ll, Fig. 2, in the block it.

The nozzle I contains a central passage i1, Figs. 1 and 4, for the plastic material, which passage terminates in a widely diverging Jet it at the discharge end of the nozzle and which serves to spread the plastic material as it leaves the nozzle to distribute-it across the die opening The temperature of the plastic material in the central passage I! may be controlled by a suitable fluid heat transfer medium circulated through U-shaped passages N, Fig. 4, at each side of the passage l'l, the medium being conducted to and away from the nozzle through pipes shown partially at 2! and 2m, Figs. 1 and 2.

The nozzle 5 also has conduits 22 associated therewith for conducting a fluid lubricant to the end of the nozzle. The conduits 21 receive lubricant from supplv'pipes 23, Fig. 2, extending from oppositesides of the nozzle and discharge the lubricant into a groove 24 formed on the exterior of the discharge end 01' the nozzle, as shown in 25 Figs. 1 and 4. This results in the lubrication of the exterior of the nozzle, thedie surfaces and the surface of the plastic shape formed in the die. The die members 1 and I embrace the.

nozzle 5 and the surfaces la and 8a, which nozzle 5 is-shaped to fit, slide back and forth on the nozzle at all times and receive lubricantv from the groove 24 and cause it to be distributed as a continuous film over the surface of the plastic shape. The lubricant may escape at both ends of the die members and drop into a drip pan".

Longitudinal slipper die members I and 8 preferably re interhtted, as shown in Fig. 3, the upper member I sliding on the lower member 40 and the lower member '8 being provided with spaced verticalguides 8b which engage the lower sides lb of the upper member. The die Qpening la is shown as formed hall. within one die member and half within the other although this is .4 not always necessary. This opening may be anyv of various shapes and in the illustrated embodiment is so designed as to form a thick strip having tapered edges.

The. bottom die member 8 slides in the bed plate ll, provided at one side with an adjustable gib 2Q, lateral adjustment of which is eflected by means of screws 21 (one only being shown) in one of the sides 28 of the bed plate.

The upper die member I is held in sliding en- 58 gagement with the lower die member I by means of gibs II bolted to the tops of the sides 2. of the bed plate II and slidably engaging the top edges of die member I.

Means are provided for effecting a transfer of heat between the slipper die members I and l and the plastic shape which is formed between them. Preferably, exchange of heat is effected in a plurality of zones formed lengthwise of the die members. In the illustrated embodiment, a heat transfer medium is circulated through the rear end of the slipper die member I through passages indicated at 3! and a separate heating medium may be independently circulated through the front portion of this die member through passages indicated at 32. Similarly, separate heat transfer media may be circulated through the rear and forward portions of the die member ii through independent passages indicated respectively at 33 and 34. Thus, the cooling or heating effect of the rear portions of the die members may be different from or the same as the forwardportions of said members.

Preferably, the sliding surfaces of the die members are lubricated topermit them to reciprocate freely. As shown in Figs. 1 and 3, lubricant may flow through pipes 35 and 38, in the rear and forward ends of the gibs 29, into grooves 31 formed on the bottom surfaces of gibs 29 to lubricate the top sliding surfaces of die member I. Each groove 31 registers with,. and delivers lubricant downwardl through, passageway 30 extending through the entire thickness of die member 1 to the bottom side thereof in order to discharge the lubricant into the die joint at 42 where the die member 1 slides on member 8.- From the die Joint 42 the lubricant may flow outwardly and downwardly through drains 43, Fig. 3, between the flanges 8!) on die member 8. The intergaging surfaces of the slide member 8 and the bed plat at 44 and 44a receive lubricant from grooves 46 in the bed plate and having supply pipes 45 and 41 connected thereto.

The die members I and-8 are reciprocated in opposite directions by the oscillation of a crank 48 Journaled on'the frame l2 and connected by an upper link 49 and bracket ii to the upper die member 'I and by a lower link 52 and bracket 53 to the lower die member 8. The crank 48 is rocked by means of a link '54 connected at its upper end to the arm 48a of the crank and at its lower end to a crank 55 on drive shaft 56 of motor 51. It will be seen that these connec. tions are such that the die plate members must be reciprocated in opposite directions.

The operation of the novel apparatus is as fol-, lows. Hot organic plastic material is delivered to the nozzle 5 and discharged from the diverging jet i8 into the die opening formed in the die members 1 and 8. The material, which may bedelivered to the pipe 6 from a suitable ram or stuifer (not shown) ma be heated to or near working temperature in advance of pipe 8 and its temperature regulated in nozzle. 5. The material flows out of the nozzle into and through the die opening saand the shape of the die opening is imparted thereto by pressure while stiffening of the material is effected by transfer of heat,

as by the application of a cooling medium in the case of a thermoplastic material or of a heating medium in the case 'of a thermosetting material. As the material is shaped, afllm of lubricant is maintained between it and the die surface by the discharge of oil' from conduits 22 through groove 24 onto the inner diesurfaces 1a and ls ascaois bers greatly reduces frictional resistance to the passage of the plastic material through the die and also insures that the lubricant will be spread over the material in the form of a film to prevent sticking.

Considerable back pressure may be maintained in the die opening without sticking because .of

the above-described provisions for lubricating and for reciprocating the die members. This helps to prevent the formation of voids or bubbles in the extruded shape and to insure that the shape will be an accurate reproduction of the shape of the die opening. The shape preferably is hardened sufliciently to be self-sustainwith each other,.said die members. having a die opening formed therein, guides on one of said die ing and to make it unnecessary to further shape material after it leaves the die.

The plastic material preferabl is caused to flow through the apparatus continuously as by delivering it from a screw stuffer rather than by means of a reciprocating ram.

The apparatus is especially useful in forming shapes of substantial thickness from such organic plastic materials as polystyrene and polymethyl methacrylate which require heating to very high temperatures and the use of high pressures to permit satisfactory shaping and which consequently have a strong tendency to stick to the die surfaces and to build up great resistance against extrusion pressure.

Having thus described the invention what we desire to claim and secure by Letters Patent is:

1. Apparatus for extruding a shape of organic plastic material comprising a nozzle, a pair of die 7 members shaped to flton and embracing said home, means supporting said die members and nozzle in horizontal position and in alignment members fitting on the other of said die members in sliding engagement therewith, and means for simultaneously reciprocating said die members in opposite directions respectively.

2. Apparatus for extruding organic plastic material comprising a horizontal extrusion nozzle, a two-part die associated with said nozzle, said die comprising upper and lower members shaped to fit on and embracing said nozzle and having an opening therein to form the plastic material to the desired shape, means including a bed plate for holding said nozzle and said members in alignment, guide means on the bed plate for slidably supporting the lower die member and guide means on the lower die member for slidably supporting the upper die member, means for applying a lubricant between said nozzle and said die members, means for applying a lubricant to the contacting surfaces between said die members, means for applying a lubricant between the bottom die member and said bed plate, and means for reciprocating said die members in opposite directions longitudinally of said nozzle.

3. Apparatus for forming a shape of organic plastic material by extrusion comprising an extrusion nozzle, a two-part die comprising members shaped to flt on said nozzle and having a die opening formed therein, a bed platehaving guides thereon slidably engaged byone of said die members, guides on the last-named die member slidably engaged by the other of said die members, means rigidly connected to said base plate and engagin the last-named die member for said die members, and means for simultaneously of the die members. Reciprocation of the mum to reciprocating said die members in opposite directions respedtlvely lbnsltudinally or the shape 7 formed therein.

4. Apparatus for extruding organic plastic materlml which comprises a horizontal matruslon nozzle, upper and lpwer die members shaped to m on and embracing said nozzle and having a die 010g formed'therem, said nozzle mm: the cross-wetioml shape or said die ope means for mounting said members in audmz -1 with mid nozzle, means 10;- holding am upper die member an sliding emwsmam with me fimver die member, means tor simulmneously reclpmcating said m memhem in opposite directions mspectlvely wngitudmmly @2 the nozzle. and ior mg a "11 M of lubricant on the inner surwas of m we members. 

